1. Field of the Invention
This invention relates to a permanent magnet consisting essentially of platinum and iron with a small quantity (less than 0.5%) of impurities and to a method of producing the same. More particularly, the invention provides a permanent magnet having an ultra-high coercive force and a very large maximum energy product, which permanent magnet is easy to work.
2. Description of the Prior Art
As permanent magnets using order-disorder lattice transformation, magnets made of an alloy consisting of cobalt (Co) and platinum (Pt) at about a stoichiometric ratio thereof have been known. At high temperatures, the cobalt-platinum alloy has .alpha. phase disordered lattice of face-centered cubic type, while at low temperatures, it has .gamma..sub.1 phase ordered lattice of face-centered tetragonal type. Accordingly, an ultra-high coercive force and a very large maximum energy product can be achieved in the initial state of transformation of the .alpha. phase disordered lattice into .gamma..sub.1 phase ordered lattice, either by cooling the alloy of .alpha. phase from high temperature of 1,000.degree. C. at a certain speed and annealing at 600.degree. C. or by quenching followed by annealing. However, the aforesaid alloy has shortcomings in that it requires a large amount of platinum, because the stoichiometric composition for providing the largest values of coercive force and maximum energy product includes 77.8 weight % of platinum, and in that its ferromagnetic atoms are cobalt atoms having a smaller magnetic moment than that of iron atoms and the magnetic properties of the alloy cannot be improved beyond certain limits such as a residual magnetic flux density of 7.2 kG (kilo-Gauss) and a maximum energy product of 12 MG.Oe (Mega Gauss.Oersted).